# physics question help on work done

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I am mostly stuck on question 8b, please help me on this.

8 Dan has a mass of 62 kg. He is travelling at a speed of 11 m s–1 at the top of a

rollercoaster loop, which is 21.8 m above the ground.

a Calculate:

i his kinetic energy at the top of the loop (1 mark)

ii his change in gravitational potential energy between the top and bottom

of the loop 0.8 m above the ground (2 marks)

iii his kinetic energy at the bottom of the loop, stating any assumption you

have made in calculating your answer (3 marks)

iv his speed at the bottom of the loop. (2 marks)

b Dan started the ride 5 m above the ground.

i Calculate the minimum work done by the accelerating force to accelerate

him to the top of the loop in part a. (2 marks)

ii Explain why the work done will be more than this minimum

8 Dan has a mass of 62 kg. He is travelling at a speed of 11 m s–1 at the top of a

rollercoaster loop, which is 21.8 m above the ground.

a Calculate:

i his kinetic energy at the top of the loop (1 mark)

ii his change in gravitational potential energy between the top and bottom

of the loop 0.8 m above the ground (2 marks)

iii his kinetic energy at the bottom of the loop, stating any assumption you

have made in calculating your answer (3 marks)

iv his speed at the bottom of the loop. (2 marks)

b Dan started the ride 5 m above the ground.

i Calculate the minimum work done by the accelerating force to accelerate

him to the top of the loop in part a. (2 marks)

ii Explain why the work done will be more than this minimum

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(Original post by

I am mostly stuck on question 8b, please help me on this.

8 Dan has a mass of 62 kg. He is travelling at a speed of 11 m s–1 at the top of a

rollercoaster loop, which is 21.8 m above the ground.

a Calculate:

i his kinetic energy at the top of the loop (1 mark)

ii his change in gravitational potential energy between the top and bottom

of the loop 0.8 m above the ground (2 marks)

iii his kinetic energy at the bottom of the loop, stating any assumption you

have made in calculating your answer (3 marks)

iv his speed at the bottom of the loop. (2 marks)

b Dan started the ride 5 m above the ground.

i Calculate the minimum work done by the accelerating force to accelerate

him to the top of the loop in part a. (2 marks)

ii Explain why the work done will be more than this minimum

**lovelyqueen**)I am mostly stuck on question 8b, please help me on this.

8 Dan has a mass of 62 kg. He is travelling at a speed of 11 m s–1 at the top of a

rollercoaster loop, which is 21.8 m above the ground.

a Calculate:

i his kinetic energy at the top of the loop (1 mark)

ii his change in gravitational potential energy between the top and bottom

of the loop 0.8 m above the ground (2 marks)

iii his kinetic energy at the bottom of the loop, stating any assumption you

have made in calculating your answer (3 marks)

iv his speed at the bottom of the loop. (2 marks)

b Dan started the ride 5 m above the ground.

i Calculate the minimum work done by the accelerating force to accelerate

him to the top of the loop in part a. (2 marks)

ii Explain why the work done will be more than this minimum

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#3

**lovelyqueen**)

I am mostly stuck on question 8b, please help me on this.

8 Dan has a mass of 62 kg. He is travelling at a speed of 11 m s–1 at the top of a

rollercoaster loop, which is 21.8 m above the ground.

a Calculate:

i his kinetic energy at the top of the loop (1 mark)

ii his change in gravitational potential energy between the top and bottom

of the loop 0.8 m above the ground (2 marks)

iii his kinetic energy at the bottom of the loop, stating any assumption you

have made in calculating your answer (3 marks)

iv his speed at the bottom of the loop. (2 marks)

b Dan started the ride 5 m above the ground.

i Calculate the minimum work done by the accelerating force to accelerate

him to the top of the loop in part a. (2 marks)

ii Explain why the work done will be more than this minimum

i. kinetic energy is 1/2mv

^{2 }= 1/2 x 62 x 11

^{2}= 3751 Joules

ii. GPE at top of loop = mass x vertical height = 62 x 21.8 = 1351.6 joules

GPE at the bottom of loop = 62 x 0.8 = 49.6 joules

iii. 1/2 x 62 x 11

^{2}= 3751 joules, assuming he isn't accelerating/ is travelling at the same speed.

iv. kinetic energy = 1/2 x 62 x velocity

^{2}

(3751 x 2)/62 = velocity

^{2}

velocity=11m/s

b)

i. change in energy = work done

energy at 5m = 62 x 5 = 310 joules

energy at 21.8m = 1351.6

change = 1041.6

work done = 1041.6

ii.there will be friction to overcome.

everything should be correct but there could be a mistake in a)iii, iv and b) ii

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